High-Tech: Auto-Ordnance M1928A1 Thompson

This a practical review of the Auto-Ordnance M1928A1 Thompson gun, with an eye towards its performance in games like GURPS, Call of Cthulhu, and Delta Green: The Role-Playing Game.


Describing the Auto-Ordnance M1928A1

The Thompson gun was envisioned by John Thompson in 1917, but much of the actual design was performed by Theodore Eickhoff. The original gun entered production as the Model 1921 in that year, made by Colt’s Patent Fire Arms Manufacturing Company of Hartford, Connecticut, under contract for the Auto-Ordnance Corporation. Despite minor variations over the course of the following 17 years, the M1928A1 adopted by the US Army in 1938 is still basically the same gun. It differs from the civilian Model 1921AC of 1926 and the Model 1928AC and the US Navy’s M1928 of 1928 in a few cost-cutting measures, including the dull Parkerized finish instead of the blueing of the earlier weapons. It also has the lower cyclic rate of the Model 1928AC and M1928. However, the M1928A1 retains most of the original features, including the finned 26.7-cm (10.5”) barrel, Lyman-made Cutts compensator, adjustable Lyman rear sight, detachable shoulder stock, and ability to use drum magazines. Practically all of these components are missing from the wartime M1 and M1A1 Thompsons. The M1928A1 normally ‒ but not always ‒ has a horizontal handguard instead of the forward pistol grip. I have fitted mine with an aftermarket forward pistol grip, which is not a perfect replica but pretty close, and allows a good fit given my size and arm length. Of course, it also provides that period feel …

Some 2 million Thompson guns were made between 1921 and 1944. Auto-Ordnance made 323,900 M1928A1s at Bridgeport, Connecticut, between 1941 and 1942. Judging from the serial number, the gun shown dates from 1941. It was apparently supplied under the wartime Lend-Lease programme to the Soviet Union with over 110,000 others, but the Krasnaya Armiya made little use of the Pistolet-Pulemyet Tompsona during the war, and the overall condition of my gun would support that. At some point, it must have been stored in some arsenal in the Ukraine, where it was forgotten for decades until the Cold War ended and the Soviet Union broke up. It was then sold to a distributor in Luxembourg, where it was permanently restricted to semiautomatic and then exported to Germany.SD_HT_M1928A1_1a

The M1928A1 is 85.7 cm (33.75”) long. It is a heavy gun, 4.88 kg (10.75 lbs) empty, 5.44 kg (12 lbs) with a full Type XX 20-round magazine, 5.6 kg (12.35 lbs) with a Type XXX 30-round magazine, and 7.14 kg (15.75 lbs) with a Type L 50-round drum magazine. By the time the M1928A1 appeared, the Type C 100-round drum infamously used by many gangsters was no longer offered. It could be used in the gun, but since only 5,000 were made, all before 1922, the things are rather scarce. The Type XXX 30-round box was introduced in 1942.

The gun’s short length of pull, short overall length, and general handiness make it a joy to handle despite the weight. Taking off the stock reduces length by 22.2 cm (8.75”) and also saves 0.75 kg (1.75 lbs). Shooting without the stock is pretty useless, although full-automatic fire from the hip could still be effective at very short distances. Taking off the stock was the modus operandi for many of the American outlaws of the 1920s and 1930s. The improved weight and concealability without the stock was more important to the gangsters than the lack of accuracy, as they typically fired at very close range and did not concern themselves with the welfare of innocent bystanders.

Filling the box magazines is very easy, but filling the drums is ridiculously involved. You have to take off the cover, place all 50 cartridges correctly inside, then replace the cover and wind up the spring by turning the handle exactly nine times. You do not want to do this under fire or with a shoal of Deep Ones approaching.


The original box magazines made by Auto-Ordnance or Seymour during WWII work flawlessly. The drums are less reliable, but work satisfactorily if filled carefully. The 2.27-kg (5-lb) 50-round drums are awkward to carry, however.

Reloading is fast with the box magazines, at least if you are right-handed. Push the conviniently-placed magazine release up with the thumb of the shooting hand. The magazine will drop free and you can insert a new magazine from below, taking care to thread it into the groove built into the front of the trigger guard. Inserting a drum magazine is more fiddly, as it needs to be threaded in from the side. This is not something you want to do under stress.

Safety and fire selector are distinct from each other, which is less useful than the modern types that combine them. The safety is sticky and difficult to manipulate, as it cannot be reached without taking off the shooting hand or employing the left hand.

Only 14.9-g (230-gr) round nose bullets should be used for optimum reliability. Recoil of the pistol cartridges is mild due to the heavy weight of the gun and the compensator. The M1928A1 is very pleasant to shoot.

The rear sight consists of a U battlefield sight with a tiny aperture and an adjustable Lyman diopter sight that has to be folded up. The latter is more useful, but was apparently not much used by historical gunners. The Thompson gun is a short-range weapon, despite the adjustable rear sight that is optimistically graduated up to 548 m (600 yards). The pistol projectile will travel to 1,555 m (1,700 yards), but its rainbow trajectory makes shots at this range pointless. More importantly, the Thompson gun uses an open-bolt action. Upon squeezing the trigger, the heavy bolt is released and travels forward under spring pressure, chambering and firing a round. This causes tremendous vibration in the gun prior to and during the release of the bullet, to the point of negating much of the aiming effort. The surprisingly good ergonomics of the weapon still allow excellent results under 25 m (27 yards) and permit combat accuracy to 50 m (55 yards) or so, but beyond that hits are unpredictable without tracers.


I use the M1928A1 primarily for static shooting at steel plates at 25 m (27 yards), but have shot IPSC rifle matches with it. I carry the magazines in a 5-pouch US Army canvas magazine carrier from WWII.

Details of the Auto-Ordnance M1928A1


  1. US Ordnance Department escutcheon ‒ crossed cannon barrels, flaming bomb and belt.
  2. Initials of the US Ordnance officer who inspected this gun ‒ WB for Colonel Waldemar Broberg.
  3. US Army designation ‒ US Model 1928A1.
  4. Actuator or charging handle. In rearward or cocked position.
  5. Serial number with Auto-Ordnance prefix ‒ AO00000.
  6. Manufacturer’s designation and chambering ‒ Thompson Submachine Gun, Calibre .45 Automatic Cartridge.
  7. Adjustable Lyman rear sight, deployed.
  8. Push button to detach the shoulder stock.
  9. Fire selector to switch between Full Auto and Single. Disabled.
  10. Safety selector to switch between Fire and Safe. In off-safe position.
  11. Magazine release.
  12. Type XX 20-round box magazine.

In Gaming

To date, I have covered the Thompson Gun in several game books. It can be found in GURPS High-Tech (2007) (p. 122), GURPS High-Tech: Pulp Guns 1 (2008) (pp. 28-30), Investigator Weapons 1: The 1920s and 1930s (2012) (pp. 87-89), and the Cthulhu Waffenhandbuch (2008) (pp. 194-195).

In GURPS, the Cutts compensator helps with firing bursts (High-Tech: Pulp Guns 1, p. 30, and GURPS Tactical Shooting, p. 76). The awkward reloading procedure of the drum magazines could result in a -2 penalty to Fast-Draw (Ammo). Drums should also receive a -1 penalty to Malf. (High-Tech, p. 155). Taking off the stock reduces Bulk but also comes with considerable penalties, reducing Acc and increasing ST and Rcl (High-Tech, p. 122, High-Tech: Pulp Guns 1, p. 29, and Tactical Shooting, p. 12). The cartridges are unsupported in the drums and tend to rattle, for a -1 penalty to Stealth.

In Call of Cthulhu, the Cutts compensator helps with firing bursts (Investigator Weapons 1, p. 88). Drums worsen the Malf from 98 to 95 (Investigator Weapons 1, p. 88). Taking off the stock comes with considerable penalties (Investigator Weapons 1, p. 88). The rattling drums halve Sneak rolls on the move (Investigator Weapons 1, p. 88).

In Delta Green, the M1928A1 does not differ from other Submachine Guns except for the Ammo Capacity.

Firearms Table

For an explanation of the statistics, see Delta Green: Agent’s Handbook, pp. 32, 54, 57, 60, 84.

Weapon Skill Base Range Damage Lethality Ammo Capacity Armour Piercing Expense
Auto-Ordnance M1928A1, .45 ACP Firearms 50 m 1D10 10% 20/30/50 N/A Unusual


At the Picture Show

Good WWII movies featuring the M1928A1 include The Devil’s Brigade (1968) and the first episodes of The Pacific (2010). The bleak Sam Peckinpah picture Bring Me the Head of Alfredo García (1974) is set much later, but still manages for the use of the gun, an M1928A1 with 30-round magazine and sling, but without stock, to feel natural.


Excellent scenes featuring Thompsons in similar configuration can be seen in various films dealing with the gangsters and outlaws of the 1920s and 1930s, eg in John Milius’ Dillinger (1973), The Godfather (1972), Michael Mann’s Public Enemies (2009), Miller’s Crossing (1990), Road to Perdition (2002), and Brian de Palma’s The Untouchables (1987). These are all-period correct for the earlier Model 1921AC and Model 1928AC, which look and perform much like the M1928A1. The Mummy Returns (2001) and Peter Jackson’s King Kong (2005) are awesome period pieces with a supernatural twist.